Gear differential



Dec. 18, 1956 s. MINARD ET AL GEAR DIFFERENTIAL Filed March 26. 1953INV-ENTORS .EV ERETT S. MINARD FREDERICK LENZEN ATTORNEY United StatesPatent GEAR DIFFERENTIAL Everett S. Minard, Glendale, and FrederickLenzen, Whittier, Califi, assignors to Librascope, Incorporated,Glendale, Calif a corporation of California Application March 26, 1953,Serial No. 344,819

Claims. (Cl. 74-675) This invention relates to gearing mechanisms, andparticularly to a gear differential which may be readily inserted in, orremoved from, equipment with which it is to be used as a unit.

Differential gears are well known mechanical expedients for combiningrotary motions in various ways.

Examples of such utilization are found in mechanical computing devices,where high precision is necessary to accurate computations, and whereWear in gears and bearings, or other service problems, may make itnecessary to replace or remove a diiferential. With previously knowndifferentials it has been necessary to disassemble large sections of theequipment to make such replacement or repair.

In the past it has not been possible to secure the full benefits ofquantity production techniques in the manufacture of gear differentials,since side gears with different sizes and numbers of teeth, anddifferent sizes of spider shafts, were required for nearly everyapplication.

The diiferential herein described makes use of a hollow spider shaft, inwhich connecting shafts of diiferent sizes and lengths may be secured.It is adapted to receive side gears of different sizes, selected to fitthe particular instrument with which the unit is to be used. The presentinvention makes it possible to apply more economical production anddistribution methods to high precision diiferentials.

The object of the invention is thus primarily an improvement 1n theconstruction of high-precision gear differentials.

Another object is the production of differentials in a form suitable forcarrying in stock as standard units, to which side gears and spidershafts may be readily added to fit the needs of a particularmanufacturer or user.

A still further object is to provide a gear differential as a unit whichmay be readily installed or removed for servicing or replacement withoutnecessitating disassembly of the associated equipment.

These and other objects may be better understood with reference to thedrawings, in which:

Figure 1 is a schematic perspective view of the differential assembly ofthe invention,

Figure 2 is an end view, taken as indicated by line 2-2 in Figure 1; and

Figure 3 is a sectional view, taken as indicated by line 3-3 in Figure2.

The differential unit 1 is formed around a hollow shaft 2, about whichis disposed a central hub or spider section 4. Hub 4 usually has anumber of symmetrically spaced stub shafts 5 projecting radially outwardtherefrom.

Annular anti-friction bearings 6 and 7 are fixed on both sides of hub 4.Hubs 9 and 10 of bearings 6 and 7 may be secured on the hollow shaft 2by any conventional means. The bearings 6 and 7 in turn have ring. gears11 and 12 secured peripherally thereon, ,by conventional means.

Ring gears 11 and 12 preferably of bevel construction, that is, each ofthe teeth 14 has a line of engagement 15 at an acute angle'to the axisof the gear. A1- ternatively, the crown or face gear types, in which theline of tooth engagement is more nearly perpendicular to the ring gearaxis, might be utilized, or a combination of straight and zerol bevelgears.

The choice of types depends on factors not material to the invention.For example, the crown gears may be somewhat more easily adjusted forproper tooth engagement, while bevel gears are somewhat simpler tomanufacture to high precision.

In the embodiment illustrated hub 4 has fixed therein three stub shafts5 directed radially outward. On each of the stub shafts 5 is disposed ananti-friction bearing 17, about which is fixed a spider pinion 19 of atype suited to match gears 11 and 12. Bearings 6, 7 and 17 may be heldin place by conventional means, such as retaining washers 20. Shims 21may be used to position the parts exactly axially of their respectiveshafts. Spring washers 22, which may bear against means such as backingwashers 23, may be used to hold the respective bearings in positionagainst the shims 21 and retaining washers 20.

Ring gears 11 and 12 are formed with mounting hub surfaces 24 and 25.Side gears 26 and 27 of any desired pitch and size may then be securedon the mounting hub surfaces 24 and 25, as shown in dotted outlineinFigure 1. These side gears may be furnished by the user, and are notconsidered a part of the difierential unit. The method of securing maybe the conventional one of expanding the side gears by heat, and thenallowing them to shrink into firm contact. For example, using side gearswith bores two to six ten-thousandths smaller than the outside diameterof the mounting hubs 24 and 25 it is possible to complete the assemblyeasily without heating the side gears hotter than the temperaure ofboiling water. Means such as a drive pin 29 may also be used to key eachof the side gears 26 and 27 into the mounting hub surfaces 24 and 25 toinsure proper alinement and prevent any possibility of slippage.

The hollow shaft 2 which may be secured to, or formed integrally with,the hub 4, constitutes the means for transmitting motion between thespider pinions 19 and mechanism with which the differential isassociated.

The connection is made by inserting a shaft 30, as shown in dottedoutline in Figure 1, into the hollow shaft 2, and clamping the twotogether. For this purpose, symmetrically disposed slots 31 may be cutin one end of the hollow shaft 2 A slotted collar 32 may then betightened about shaft 2 by means such as a cap screw 34. Alternativemeans, not illustrated, may be used in which the slotted end of hollowshaft 2 is threaded, and a clamping nut screwed on to compress theslotted portion and complete the connection. In either case, releasingthe slotted portion from compression permits the shaft 30 to bewithdrawn. The entire differential unit may then be readily removed fromits location in the associated mechanism.

It will be seen that this construction makes possible a greatflexibility in use of the diiferential as a unit, since the user is notlimited by particular sizes and lengths of shafts connected to thespider, as has been the case in prior difierential assemblies.

In alining and adjusting the differential elements, it is necessary tobe able to fix the rotational position of the spider. This isaccomplished with the aid of one or more locking bores 35 formed in thehub 4. A rod or equivalent implement, not shown, may be inserted intothe bore 35 to hold the spider in the desired location or rot te it withre pec to. .a locked support shaft. A plurality of such bores 35 may bedisposed symmetrically about the hub 4 for convenience if desired, sothat adjustments may readily he made. various positions of the spider. a

lnaddition :to. the lease: of removing -.the -.d ifierential unit, theslotted end and collar i32permits the'relative' angular. adjustment-ofthe difiIerential hollow shaft and the mounting shaftin an infinitevariety of angularrelationships. This is important in the use of thesedifferen tials in computing machinesjwhere'high precision is required.

We claim:

'1. In .a differential .gear assembly of the characterdescribed, ahollow shaft having :a resiliently deformable end portion provided with;a plurality of symmetrically disposed slots, a differential gearassembly carried bysaid hollowshaft beyond the inner ends of said slotsand comprising .a pair of ring gears vrotatably mounted on said hollow-shaft,'each of said ring gears being provided with an external shoulderfor receiving a spur.

gear, a spider fixed to. said hollow shaft between said ring gears, aspider gear meshing with .said ring gears,

1 clamp means for resiliently deforming inwardly the slotted end portionof said hollow shaft to secure the' same to a support shaft passingthrough in any desired angular relation with respect to said supportshaft, and means carried by said spider engageable by a tool wherebysaid hollow shaftmay be adjusted with'respect to' said support shaft tofacilitate engagement of spur gears carried by said shoulders of saidring gears 'With locked gears arranged for meshing relationship theretively prevented from rotational, movement to said ring gear. ,7 a

4. In a difierential gear assembly ofthe character in respect described,a hollow shaft having a resiliently deformable portion thereof, adifferential gear assemblylcarried by said'hollow shaft and comprising apair of ring gears rotatably mounted on saidhollow shaft, each of said.ring gears being provided with an external shoulder for receiving a spurgear, a spider fixed to said hollow shaft between .said ring gears, aspider gear meshing. with: said gears, means for resilientlydeforming-inward ly the deformable portion of said hollow shaft toadjustably secure the same to a shaft passing therethrough,

and means carried by said spider engageable bya tool whereby said hollowshaft may beadjusted with respect i to said support shaft to facilitateengagement of spur 7 gears carried by said shoulders of said ring gears.with

locked gears arranged for meshing relationship therewith.-

.5. In a differential .gear assembly of the character 7 described, ahollow shaft having a resiliently deformable .portion thereoffadifferential gear assembly carried by said hollow shaft and comprising apair of ring gears rotatably mounted on said hollow shaft, each of saidring gears being provided with an external shoulder for receiving a spurgear, a spider fixed to said hollow shaft between said ring gears, aspider gear meshing V V with said ring gears, means for resilientlydeforming inwardly the deformable portion .of' said hollow shaft toadjustably secure the same to a shaft passing therethrough, and meanscarried .by said spider whereby'said hollow shaft may be adjustedW'rthrespect to said sup- 7 port shaft.

7 References Cited in the file of this'patent' UNITED STATES PATENTS 7,

217,068 Cranston j July 1, 1879 299,886 Westbrook June 3, 1.8841,155,589 McDonald Oct. 5, 1915 1,780,745 Eckart Nov. 4, 1930' 2,347,259

Groene. Apr. '25, 1944

